The intelligent, slightly-spoiled daughter of the owner of a successful paper merchant, Alan (Denis Lill) and his wife Pam (Wanda Ventham), Cassandra was an ambitious employee of the local bank. She made her first Only Fools and Horses appearance in the episode Yuppy Love, in which she was an attendee of Rodney's adult education class. The two first met when they accidentally mixed up their raincoats in the cloak room, and met again at a disco later that night, at which Rodney's friends Mickey Pearce and Jevon unsuccessfully ask her for a dance. Rodney then bet £20 that he would be successful and, to their horror, she agreed to dance with him. Cassandra also offered to give him a lift home, and they exchanged telephone numbers. However, as he was ashamed to take her home to Nelson Mandela House, he pretended he lived in a more upmarket location on King's Avenue and was duly left stranded as it began to pour with rain, again getting their coats mixed up leaving Rodney to walk home.
Their relationship blossomed throughout the sixth series; In The Unlucky Winner Is... she went to Spain with Rodney and Del, and had to pretend to be Del's wife, and Rodney's stepmother. In Sickness and Wealth, Rodney announced that they were engaged; they married in the final episode of series 6: Little Problems, after which they moved into their own flat. Her marriage to Rodney was not without its problems; Rodney was envious of Cassandra's privileged upbringing and her qualifications. When Cassandra wanted to build herself a career at the bank, Rodney was outraged, as he wanted her to be little more than a housewife, and have his dinner on the table for when he got home from work.
After a year of being married she and Rodney split up in The Jolly Boys Outing (the 1989 Christmas special), when he punched her boss and broke his nose. In the next episode aired Rodney Come Home (Christmas special 1990), they broke up again, which started an ongoing split between the pair. This split carried on throughout the duration of series 7. In The Chance of a Lunchtime Del played matchmaker between the two, reuniting them. However, the two were only together for an hour before Cassandra saw Rodney with an ex-fiancē of Del Boy's. Assuming that Rodney was cheating on her, Cassandra locked him out of the flat. They were ultimately reconciled in Three Men, a Woman and a Baby but after just getting back together they were interrupted by a phone call that Raquel had gone into labour and Del wanted Rodney to be there for the birth. The episode Miami Twice saw them trying to patch up their relationship, and in Mother Natures Son they were back together properly, and stayed together ever since. The later episodes saw them attempting to conceive a child, and Cassandra was promoted to head of small business investment at the local bank. After suffering a miscarriage in "Modern Men", she and Rodney later had a daughter, Joan (named after Del and Rodney's late mother), in Sleepless in Peckham.